1. Field of the Invention
The present invention relates to an image recording apparatus for recording an image on a recording medium by ejecting ink from ink ejection nozzles based on inkjet technology. More particularly, the invention relates to an image recording apparatus which applies a pre-processing agent to a recording medium before ejecting ink to record an image on the recording medium.
2. Description of the Background Art
In an image recording apparatus for recording an image based on inkjet technology, an ink ejection failure occurs in some cases because ink ejection nozzles are clogged or air bubbles enter an ink supply path. A variety of methods have been proposed in the past to detect an ink ejection nozzle suffering the ejection failure.
An example of such methods is known in which ink is ejected from a plurality of nozzles for forming adjacent dots or neighboring dots at different times to print a test pattern and a determination as to whether each of the nozzles ejects ink well or not is made from the result of printing. This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-66650 (1997).
On the other hand, there is a method in which, before an image recording apparatus records an image on a recording medium poor in ink fixability, that is, a recording medium having low ink absorbency, an ink receiving layer for enhancing the fixability of ink to the recording medium is applied onto the surface of the recording medium. An example of this method is known in which, prior to the recording of an image, a pre-processing agent which is a material constituting the ink receiving layer is applied onto an arbitrary region on the recording medium based on inkjet technology. This method is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-58930 (1999) and Japanese Patent No. 3372681.
A pre-processing agent less visible (e.g., transparent or substantially transparent) than the ink for use in image recording is often used when the pre-processing agent is ejected and applied onto the recording medium based on inkjet technology, as in the techniques disclosed in Japanese Patent Application Laid-Open No. 11-58930 (1999) and Japanese Patent No. 3372681. It is also important to detect an ejection failure in nozzles (pre-processing agent ejection nozzles) for ejecting such a pre-processing agent.
However, the use of the above-mentioned method of printing the test pattern as disclosed in Japanese Patent Application Laid-Open No. 9-66650 (1997) to detect the ejection failure in the pre-processing agent ejection nozzles presents a problem to be described below. When the less visible pre-processing agent is used, it is difficult to discriminate between a region coated with the pre-processing agent ejected from a normal nozzle and a region not well coated with the pre-processing agent because of the ejection failure in a nozzle. This makes it accordingly difficult to detect the nozzle suffering the ejection failure.